This invention relates to gravity conveyors. More particularly, the invention relates to order picking and assembly lines that are supplied and supported by gravity flow lanes.
Many trade articles are unitized into standardized modules for market transport and delivery. A module may constitute a compactly aligned and stacked assembly of numerous smaller units on a portable platform called a pallet. Furthermore, competitors within a single industry, such as for bottled beverages, will cooperate to standardize the size and shape of their product market packages to facilitate filling and handling by automatic machinery.
Warehouse storage of articles on pallets or modular containers is further facilitated by low friction pallet support platforms. These low friction platforms are often a multiplicity of parallel planar lanes set along a shallow slope such as 0.4 to about 0.5 in./ft. Each lane width is usually sufficient for only one line of modules or pallets. The low friction surface is usually provided by a multiplicity of small wheels or rollers supported on anti-friction on bearings for rotation about parallel axes. Conceivably, however, other forms of low friction surface may be used such as air-bearing tables.
The functional objective of these sloped, low-friction pallet lanes is to exploit gravity for movement of the warehouse stock. For an inventory management that desires the "first in first out" principle, newly arrived inventory is placed on a sloped pallet lane at the upper end and inventory to be removed is withdrawn from the low end of the lane. A queue of modules or pallets, terms hereafter used interchangeably and synonymously, advance by gravity alone from the high end to the low end of a lane without external power.
Such low friction surface lanes have come to be known and characterized in the art as "gravity conveyors", "flow rails" and numerous similar terms and phrases.
Controls over such flow rails are usually limited and simple in principle. For example, velocity of a module along a flow rail is often restrained by conveyor surface support rollers having centrifugal drag braking. Manually or automatically engaged chocks may be used to prevent downward movement of modules past a predetermined point until desired.
In a separate but related practice, product distribution warehouses may draw from a multiplicity of individual product storage lanes to assemble a specified order. This order assembly process and practice is often characterized in the art by the term "picking". A specified order is assembled by picking and choosing from among many available offerings. These offerings may be presented for picking convenience by gravity flow rails. For example, each of products A, B and C may be packaged in standardized units whereby four units may be aligned in a single tier plane above a pallet surface. Additionally, four tier planes of these units may be stacked vertically above the pallet surface for a full module comprising sixteen units of the product.
Representatively, an order may specify four units of product A, four units of product B and eight units of product C. Assembly of the order will therefore draw one pallet tier from the product A supply lane, one pallet tier from the product B supply lane and two pallet tiers from the product C supply lane. These four tiers are vertically assembled on a single order pallet for delivery to the buyer.
To expedite the picking process, powered grapples called "pickers" that are carried by overhead lifts or warehouse trucks have been devised to grasp, lift and transport one or all of the product tiers on a pallet, simultaneously. Implements such as the Tygard Claw.RTM. manufactured by the Tygard Machine and Manufacturing Co. of Washington, Pa. are representative. However, the reliable operation of such implements is predicated on a level planar alignment of the tiers. Since the alignment of several product units, within a tier includes no structural connection therebetween, only continuous surface friction between the units of a tier holds the tier together under the compressive grip of the grapple implement. A planar misalignment of a pallet tier with the picker grapples by the magnitude of a gravity flow slope exceeds the capacity of the implement. Hence, use of a picker to assemble specified orders from a gravity flow rail has required that the actively picked pallet in a product flow rail be removed from the flow rail lane and placed on a level surface that is accessible to the picker.
Traditionally, this removal and repositionment of a picked pallet to a level surface has required selectively applied power, such as a powered conveyor or a manually operated warehouse truck.
It is, therefore, an object of the present invention to provide gravity motivated transition of a flow rail module onto a level surface.
Another object of the invention is a picking system having a substantially self-regulating transfer of modules from a gravity flow rail to a level surface.